Substantial technological improvement in the field of electronics over past years has enabled computer equipment manufacturers to provide powerful, fully-featured computers that are compact and portable. So-called "laptop" or "notebook" type computers have proven to be extremely popular in recent years, and a wide variety of such computers are known and commercially available.
A portable computer apparatus will typically have at least some subset of the following components: a housing for containing the computer circuitry and other electronic components; a power source (e.g., a battery) or at least a cable for connecting the apparatus to a source of power; at least one means for accepting user input (e.g., an alphanumeric keyboard, a "mouse", or the like); and output means (e.g., a text and/or graphic display, a printer, or the like) for communicating information to the user. In addition, portable computer equipment will frequently be equipped with data storage devices, such as a floppy disk drive or a hard disk drive. While some set of these components can be found in any portable computer equipment, there is a nearly endless variety of ways that they can be arranged.
There are a number of design considerations that are of particular concern in the context of portable computer equipment. In general, it is preferable for a portable computer apparatus to be durable and ruggedly constructed, since it should be expected that a portable computer will be picked up, carried about, jostled, and even dropped occasionally. Moreover, while the size and weight of portable computer equipment is preferably kept to a minimum, this is preferably not achieved at the expense of making components like the display, keyboard, or battery too small, or at the expense of making structural components weak and easily broken.
Ergonomic factors should also be considered in the design of portable computer equipment. For example, some portable computers, such as the Compaq SLT, are provided with detachable keyboards so that a user can position the keyboard conveniently for typing without having to move the entire computer. Also, portable computers often are equipped with a display screen that can be manipulated into a variety of orientations so that it can be easily viewed by the user from different angles. This is particularly important with liquid-crystal displays (LCDs), which are typically more difficult to view at oblique angles.
One common way in which portable computer manufacturers satisfy the requirements of portability, ruggedness, and ergonomic convenience is by providing a hinged display screen that can be folded down and secured onto the top of the computer housing, thereby protecting the screen and reducing the size of the apparatus when not in use. When opened, the hinged display screen can be adjusted over a range of viewing angles so that the user can select a convenient one. As a further expedient, the closed hinged display can serve as a protective structure for other components, such as the keyboard. Such a configuration is described in U.S. Pat. No. 4,903,222 to Carter et al. entitled "Arrangement of Components in a Laptop Computer System", which patent is incorporated herein by reference in its entirety.
A portable computer having an hinged display screen which folds down over an alphanumeric keyboard is also disclosed in U.S. Pat. No. 5,090,913 to Kobayashi; in U.S. Pat. No. 5,016,849 to Wu; in U.S. Pat. No. 5,052,078 to Hosoi; in U.S. Pat. No. 4,976,007 to Lam; and in U.S. Pat. No. 4,960,256 to Chihara et al.
In addition to the various types of general-purpose portable computer equipment that are known and commercially available, there are also many different types of special-purpose, portable computer devices. Such devices may have many of the same components found in general-purpose computers, but may also have additional components, depending upon the specialized purpose for which they are intended. The class of special-purpose portable computer equipment may include such devices as service or test equipment carried by field service technicians; data storage and acquisition carried by delivery persons, meter-readers and the like; portable communications devices; and of particular relevance to the present invention, computerized programmers for implantable medical devices and the like.
Implantable medical devices, such as cardiac pacemakers, cardiac defibrillators, neural stimulators, and the like, are often programmable in their operation by means of a radio-frequency telemetry link established between the device and an external programmer unit. In the case of cardiac pacemakers, for example, a clinician may, through the use of an external programmer, control such parameters as pacing rate, pacing mode, sensitivity, pacing output, and the like, in a pacemaker implanted in a patient. Pacemaker programmers are preferably portable, so that they may be conveniently transported from patient to patient in a hospital, or even taken to a patient's home or to another non-hospital setting. Portability is also desirable due to the possibility that the programmer may be needed in an emergency situation, e.g., when the patient is undergoing surgery in an operating room. A variety of different programmable pacemakers, and external programming units therefor, are known and commercially available.
A programmer for non-invasively programming a cardiac pacemaker is described in its various aspects in the following U.S. Patents to Hartlaub et al., each commonly assigned to the assignee of the present invention and each incorporated by reference herein: U.S. Pat. No. 4,250,884 entitled "Apparatus For and Method Of Programming the Minimum Energy Threshold for Pacing Pulses to be Applied to a Patient's Heart"; U.S. Pat. No. 4,273,132 entitled "Digital Cardiac Pacemaker with Threshold Margin Check"; U.S. Pat. No. 4,273,133 entitled Programmable Digital Cardiac Pacemaker with Means to Override Effects of Reed Switch Closure"; U.S. Pat. No. 4,233,985 entitled "Multi-Mode Programmable Digital Cardiac Pacemaker"; and U.S. Pat. No. 4,253,466 entitled "Temporary and Permanent Programmable Digital Cardiac Pacemaker".
Aspects of the programmer that is the subject of the foregoing Hartlaub et al. patents (hereinafter "the Hartlaub programmer") are also described in U.S. Pat. No. 4,208,008 to Smith, entitled "Pacing Generator Programming Apparatus Including Error Detection Means" and in U.S. Pat. No. 4,236,524 to Powell et al., entitled "Program Testing Apparatus". The Smith '008 and Powell et al. '524 patents are also incorporated by reference herein in their entirety.
A telemetry system for communicating information, either in analog or digital form, between an implanted device and an external programming apparatus is disclosed in U.S. Pat. No. 4,374,382 to Markowitz entitled "Marker Channel Telemetry System for a Medical Device", and in U.S. Pat. No. 4,556,063 to Thompson et al., entitled "Telemetry System for a Medical Device". The Markowitz '382 and Thompson et al. '063 patents are commonly assigned to the assignee of the present invention and are both hereby incorporated by reference in their entirety.
Implanted devices in general have improved in their sophistication and functionality over the past years, and it has become increasingly more important for a physician or clinician to be able to interrogate the device to determine its operational status, and to be able to communicate numerous commands and parameters to the device in order to control various aspects of the device's operation. Improvements in the telemetry system, as reflected, for example, in the above-reference Thompson '063 patent, have enabled a great deal of information to be readily and quickly exchanged between the implanted device and the external programming unit. In some cases, a real-time electrocardiogram (ECG) signal may be transmitted from the implanted device to an external unit, so that the physician can monitor the patient's heart activity and the effects of pacing pulses thereon. A pacemaker system having such capability is described, for example, in U.S. Pat. No. Re. 32,361 to Duggan, entitled "Implantable Telemetry Transmission System for Analog and Digital Data", assigned to the assignee of the present invention and incorporated into the present disclosure by reference in its entirety.
Given the level of sophistication and functionality of state-of-the-art pacemakers, it has become necessary for the operational capability of external programming units for such pacemakers to be similarly improved. For example, since pacemakers are known which are capable of transmitting real-time ECG signals to an external unit, it would naturally be desirable for the external unit to be able to visually display the ECG signal, without the need for additional wiring or equipment.
In addition to the above-discussed considerations that should be taken into account in designing a portable, general-purpose computer, there are certain factors that are of particular importance in the context of medical device programming units. A medical device programming unit should be simple to operate, highly reliable, and well adapted for use in an operating room or other clinical setting.